Clutch Mystery

[Roland Stone]

Please see:  Brammo Empulse FAQ - Re:  2014 Brammo Empulse $1000

Regarding the above referenced post I would appreciate knowing if anyone has experienced a clutch that stops engaging for no apparent reason as with my Empulse clutch.  The clutch worked perfectly last time the bike was ridden.  A couple of weeks later I went on another casual ride and immediately there was no clutch engagement.  Bled the clutch two different occasions and still no engagement.  Finally into a ride after the 2nd bleed, the clutch suddenly started working again which would appear not to indicate air in the line.  Any ideas would be appreciated.

[siai47]

The hydraulic system disengages the clutch, not engages it.  Therefore with a failure (or air in the system) the clutch would be engaged at all times.  Something else is going on.  On my bike, it is almost impossible to disengage the clutch when cold and even when warm there is some drag on the clutch due to oil between the clutch plates.  I hate to sound like I am questioning you on what happened but it almost seems like the transmission wasn't engaged in any gear---possibly in between two gears due to a shift fork or shift drum problem or a timing problem in the shifter. I only wish my clutch would fully disengage  !

[Roland Stone]

siai47 – Thanks for the response. As you noticed I know nothing about MC clutches however researching Google I did at least discover the Empulse has a “wet” type clutch typical in motor cycles. I have found nothing in any Brammo parts/servicing-maintenance documents providing/describing operational Empulse clutch details.

I live in Florida half way down the east coast so in my situation I don’t think ambient temperature would have anything to do with my clutch issue.  I also read on Google that the motor oil used can affect wet-clutch operation/performance reference friction quality and additives. My 2014 Empulse presently has 950 miles on the clock and I’ve used Repsol Moto 4T Racing 10W30 since new. Wondering if the oil could be a contributing factor? When the clutch was not working, in a stopped/throttle-off situation I could shift up/down through all the gears with or without pulling in the clutch handle. To clarify, my clutch is now and suddenly (mysteriously) working again. I can again downshift as normal and the tach indicates the slight RPM change in the process whereas before when the clutch wasn't working, there was no RPM change when pulling in the clutch handle (disengaging).
 
My shifting technique uses the clutch for downshifting and only occasionally on the upshift. Also I never exceed 3000 RPM until the motor temp is above 80F. My Empulse has never been on a major freeway and my operational speed is rarely over 60 MPH in my local driving. All that in mind, I would think a mechanical problem in the clutch would not be intermittent which would lead me to believe my clutch problem has something to do with my driving and or the oil I’m using.  As I said, it’s a mystery and I’ll entertain any suggestions.   

[Ndm]

One possibility is that there's moisture buildup and it's made it's way to the slave cylinder, resulting in a small rust buildup causing the slave cylinder piston to stick in the cylinder, as a mechanic I see this sometimes with brake master cylinders, after a brake job the piston goes past the rust buildup causing the rubber cups to tear or score when pumped past it's normal travel resulting in a now inoperable master cylinder, explaining that to a customer is always fun, my suggestion is that you do another pressure bleed with new good quality brake fluid and just keep applying the clutch several times to flush the old fluid out, if it has torn the cups no amount of bleeding will help and you will need a slave cylinder, good luck and I hope it works out for you!

[siai47]

Sounds like you are doing everything right.  The oil you are using would be correct for the "wet" clutch.  However your further description of the problem is confusing to me.  When you say you can shift through the gears with the motor stopped and the clutch not pulled in---this is normal operation.  With the clutch lever released, in normal operation the bike would move any time the "throttle" is turned.  Even with the clutch pulled in from a stop there is some tendency to move due to the stiction of the clutch discs caused by the oil between the drive and driven plates in the clutch.  This is more noticeable when the transmission oil is cold (thicker) then when it is hot. 

It is possible (as an earlier poster suggested) that something is corroded or sticking in the clutch release system.  When you pull in the clutch lever, you are applying hydraulic pressure to a piston located on the transmission that moves a rod that runs through the transmission to the clutch.  The clutch has a spring loaded pressure plate that compresses the drive and driven plates of the clutch together to connect the motor to the transmission gears by friction.  The rod pushes on a plate lifter to overcome the pressure plate springs thereby allowing the drive and driven plates to spin in relation to each other preventing the transfer of power from the motor to the transmission.

Even with the clutch stuck in the fully released position, there should be some tendency for the bike to want to move due to the oil between the plates.  The clutch used in the Empulse seems prone to this when cold so your clutch shouldn't be any different.  You have flushed the hydraulic system so you are good to go there.  You should change the transmission oil (again) and see what the color of the drained oil looks like and how much "fur"" (metal particles) you find on the drain plug.  Dark or black oil usually indicates you are overheating clutch material.  In any event, if the motorcycle moves with the clutch lever released and the tach isn't spinning off the dial, you don't have a clutch engagement problem.  If it there is no RPM change on the tach if you pull in the clutch when driving and you apply throttle, then you have a disengagement problem.  As the clutch breaks in you might be seeing normal operation for the first time.

[Roland Stone]

Thanks to you both for your advice and analysis and as well for some needed clutch education.  Have already changed my oil at least three times since I’ve had my Empulse but will do another oil change this weekend and have a good look at the waste oil and mag oil plug.  Hopefully my clutch anomaly is just a function of the break-in period as suggested.  Will post again on the topic if there's any more drama.